Ordinary removable dentures, dental plates and the like, comprise teeth mounted in a suitable plate or base. Denture adhesives or stabilizers are used to provide a cushion or gasket between the denture and the gums or tissues and to fill the interstices between the dentures and the gums or tissues.
Denture stabilizing or adhesive compositions can exhibit several deficiencies. Aesthetic deficiencies may include oozing of the adhesive from under the dental plate during insertion and throughout the wearing period and messiness and difficulty of removing the residual adhesive from the mouth and dentures. Additionally, food may become trapped between the denture and the oral cavity of the wearer. Considerable effort has been made over the years to develop denture adhesive compositions with improved holding capabilities which are aesthetically pleasing and easy to use.
Lower alkyl vinyl ether-maleic copolymers and salts thereof are known in the art for use in denture adhesive compositions. Such disclosures include: U.S. Pat. No. 4,980,391 to Kumar et al., issued Dec. 25, 1990; U.S. Pat. No. 5,073,604 to Holeva et al., issued Dec. 17, 1991; and U.S. Pat. No. 5,525,652 to Clarke, issued Jun. 11, 1996.
Technologies comprising crosslinked alkyl vinyl ether-maleic copolymers providing absorbent fibers and adhesives have also been taught in the art. Examples include: U.S. Pat. No. 3,983,095 to Bashaw et al., issued Sep. 28, 1976, disclosing a method for preparing water-insoluble, water-swellable fibers by reacting a copolymer of maleic anhydride and a cross-linking agent; U.S. Pat. No. 2,866,775 to Sellers, issued Dec. 30, 1958, disclosing adhesive compositions comprising esters of maleic anhydride and vinyl ether copolymers optionally crosslinked with glycols; and U.S. Pat. No. 5,049,235 to Barcus et al., issued Sep. 17, 1991, disclosing absorbent fibers comprising a cellulosic fiber, a poly(methyl vinyl ether-co-maleate) copolymer and a polyol, all of which are chemically bonded together. Layered denture adhesive compositions have also been disclosed in, for example, U.S. Pat. No. 4,880,702 to Homan et al., issued Nov. 14, 1989 and European Patent Application 0,353,375 to Altwirth, published Feb. 7, 1990.
Despite the above-noted technologies, as well as others, a need still exists for denture stabilizing compositions providing improved hold and aethestics.
In accordance with the present invention, it has been discovered that denture adhesive compositions comprising a non-adhesive self-supporting layer and partial salts of lower alkyl vinyl ether-maleic acid copolymers lightly crosslinked covalently with an organic crosslinker provide superior denture stability and retention over a significantly longer period of time versus conventional denture adhesives. Specifically, the compositions exhibit higher resistance to salivary washout while maintaining the same or better denture hold as conventional denture adhesives. This added resistance to salivary washout translates to longer denture hold and stability. It is believed that the low level of covalent crosslinking of the partial salt of a lower alkyl vinyl ether-maleic acid copolymer distinguishes the present invention from other technologies utilizing crosslinked alkyl vinyl ether-maleic acid copolymers or their partial salts.
Therefore, it is an object of the present invention to provide partial salt lower alkyl vinyl ether-maleic copolymers which are lightly crosslinked with an organic crosslinker, which are delivered on a non-adhesive self-supporting layer vehicle. It is also an object of the invention to provide an improved adhesive compositions which may be used with dentures and provide a firm hold and exhibit higher resistance to salivary washout.
These and other objects of the present invention will become readily apparent from the detailed description which follows.